1: along the way you will at least once start to question your innate ability to learn this stuff. That is natural and realize that the reason e.g. mathematics has the reputation of being something you either "get" or not is that there is no method, as of yet, out there to train for mathematics systematically like there are methods for learning, say, how to play the piano.

2. Focus on building the right mental representations of the concepts. If you want to learn, say, differentiation, don't just learn all the differentiation rules like dx^n / dx = nx^(n-1). Try to understand the definition of differentiation. In school they usually don't teach you how to think about this stuff, they only teach you to manipulate algebraic symbols. Newton himself believed algebra was just of expressing what you already understand, not a way of understanding things in itself. I think that is very true.

3. The most important thing is mental representation. You sometimes see self-taught people try to answer questions on math.stackexchange and whatnot, and they are usually easy to spot because they don't have a real mathematician's mindset. They learned the lingo and the techniques but they haven't learned how to think properly about the concepts. So, to avoid becoming like that, get as much interaction with skilled mathematicians as possible. If you don't have access to them physically, one way is to ask and answer questions on math.stackexchange. People there enjoy punishing sloppy mathematics, and that is very good.

4. Engage in a process of trial and failure where the failures are explicitly identifiable. Solving practice problems where you have access to the answers is a decent method for that, I guess. But look very closely at what exactly went wrong whenever you made mistakes. There is really no way of learning anything unless you get feedback. And you cannot any feedback unless you do things that can generate mistakes. For example merely reading stuff is *not* a way to learn mathematics. You have to get your elbows in the mud. It's definitely not a pleasurable process, but it's the only way.

5. Have specific goals. Set up the broad topics you want to learn, and what sort of problems you would want to solve within each one. That is obviously hard to know in advance, but you can do this by looking up curriculums of university courses in Calculus. Typically, they will probably include:

- Real numbers and continuity

- Sequences, series and limits

- Differentiation

- Integration

I don't have any suggestions for specific books on Calculus, because there are so many of them. But if you plan to enroll at some specific university, I would simply look up the books they use and use that as a starting point.

There is a lot to say about the best way to learn this stuff and I am probably forgetting a lot. Feel free to ask more questions. But they key elements are:

- Observe how skilled mathematicians think

- Get your elbows in the mud with a process based on trial-and-error *with* feedback

- Have specificity in your goals